Voice coil for radio loud-speakers



Jan..16, 1951 R. K. Y. KIM 2,538,691

VOICE COIL FOR RADIO LOUD-SPEAKERS Filed July 19, 1948 awe/M1041Patented Jan. 16, 1951 UNITED STATES JNT DFFICE 1 Claim. 1

This invention relates to loud speakers.

An object of this invention is to provide in a loud speaker of that typeembodying a vibratory diaphragm or cone which will practically eliminateinherent distortion and at the same time provide high power handlingcapacity.

Another object of this invention is to provide in a loud speaker, avibratory diaphragm or cone wherein the reflected impedance to the lineor tubes will be negligible, the frequency response will be improved,and the bass and treble overtones which were heretofore lost ordistorted will be made audible and free from distortion.

A further object of this invention is to provide an improved loudspeaker wherein the response is linear with input over the entire audiofrequency range.

With the above and other objects in view, my invention consists in thearrangement, combination and details of construction disclosed in thedrawings and specification, and then more particularly pointed out inthe appended claim.

In the drawing:

Figure 1 is a fragmentary vertical section of a loud speaker embodyingthis invention;

Figure 2 is a fragmentary sectional view taken on the line 22 of Figure1.

Referring to the drawing, the numeral in designates generally a loudspeaker which includes an electro-magnetic member ll having an iron coreI2 extending therefrom and projecting loosely into an opening l3 whichis formed in a plate I4. A cone or diaphragm i5 is supported by flexiblesupporting means it from the plate l4 and includes a cylindrical centraltubular portion I! projecting loosely into the opening [3 and engagingloosely about the iron core H2.

The tubular member I! has wound thereabout a coil I8 and there isinterposed between the coil 18 and the outer surface of the tubularmember H a metallic film or coating Hi. This film or coating I 9 isformed of powdered iron and as shown in Figure 1 the coating is extendsunder the entire length of the coil I8.

A second metallic coating or film 20 is disposed about the outer surfaceof the coil l8 and also terminates at a point forwardly from the rearend of this coil. The outer coating 2i! is of such thickness that therewill be maintained an air gap or space 2| between the coating 2 and thewall of the opening !3. The two coatings I9 and 28' are connectedtogether by a connecting coating 22, and the connected coatings have theeffect of creating a high magnetic flux density area adjacent the voicecoil i8 for the currents of the voice coil to react on. These coatingsalso 2 compensate for the difference in magnetic densities with respectto the front and rear, because in uncoated speakers the magneticdensities are usually greater at the rear. The coil I8 is com- I monlyknown as the voice coil and is disposed in the magnetic fiux generatedbetween the core member l2 and the plate l4. With a voice coil having apartial coating and lining as hereinbefore described, the loud speakerwill have a higher degree of efliciency with negligible inherentdistortion and the power handling capacity of the speaker will behigher. Furthermore, the reflected impedances will be negligible to theline or tubes and there will be a better or increased frequencyresponse, particularly in the bass overtones and the treble overtoneswhich have heretofore either been lost or distorted.

The term diaphragm as herein set forth and claimed will include bothadiaphragm member and a cone which is supported from a flexible supportso that the cone will be subjected to the vibrations caused in operationof the loud speaker.

I do not mean to confine myself to the exact details of constructionherein disclosed but claim all variations falling within the purview ofthe appended claim,

What I claim is:

In a loud speaker having an electro-magnetic member, an electro-magneticcore extending therefrom, with an apertured plate about a portion of thecore and a diaphragm extending from said plate having a cylindricalcentral portion projecting into the aperture in said plate about saidcoil, a voice coil wound about said central portion within saidaperture, a powdered iron film interspersed between the inner side ofsaid coil and said central portion, a second powdered iron filmsurrounding only a portion of the outside of said coil, said portionbeing of less than one half the length of the coil at the end thereofremote from the electro-magnetic member, and a connecting film betweenthe edges of said first and second film over one end of said coil.

RICHARD K. Y. KIM.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,921,924 Hunter Aug. 8, 19331,976,874 Brzeski Oct. 16, 1934 2,164,374 Barker July 4, 1939

